Author(s): A; Lka S; Ingh; Florian Seitz; Christian Schwatke
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Abstract: In this study we apply geometrical and gravimetrical observations from various Earth observation satellites in order to estimate the variability of the Aral Sea with respect to its geometrical extent and the water storage. Due to the diversion of its primary inlet rivers for irrigation purposes the lake suffered a devastating decline until its south eastern part had almost dried out in 2009. We present the change of the lake’s surface extent based on optical remote sensing data from Landsat images that are analyzed for spring and autumn each year. Height variations of the lake surface are computed from multi-mission satellite altimetry. Both the surface extent and the water stage of the lake reached an absolute minimum in 2009 autumn. However in 2010 a clear reversal of the negative trend of the previous years is visible. A geometrical intersection of the water level with a digital elevation model allows for estimating water volume changes. The resulting volume changes are subsequently analyzed with respect to satellite-based estimates of mass variations observed by the satellite gravimetry mission GRACE. The results reveal that water storage variations in the Aral Sea are indeed the principal contributor to the GRACE signal of mass variations in this region. It is shown that the different observations from all missions agree very well with each other with respect to their temporal behavior.
Year: 2012